The present invention relates to electric vehicles, and more particularly to an all-electric vehicle system that is powered from an onboard high-specific-power energy storage device, and that receives power to charge the energy-storage device inductively through coils in the roadway over which the vehicle travels. The invention further relates to enhancements included within such a roadway-powered electric vehicle system, such as an automatic position-determining system, automated vehicle guidance, demand-based vehicle dispatch, and the like.
In recent years, there has been an increasing emphasis on the development of an all electric vehicle (EV) or other zero emission vehicle (ZEV). The goal, as mandated by many governmental jurisdictions, is to have a certain percentage of all vehicles be zero-emission vehicles. Advantageously, zero-emission vehicles do not directly emit any exhaust or other gases into the air, and thus do no pollute the atmosphere. In contrast, vehicles that rely upon an internal combustion engine (ICE), in whole or in part, for their power source are continually fouling the air with their exhaust emissions. Such fouling is readily seen by the visible xe2x80x9csmogxe2x80x9d that hangs over heavily populated urban areas. Zero-emission vehicles are thus viewed as one way to significantly improve the cleanliness of the atmosphere.
In the State of California, for example, the California Air Resources Board (CARB) has mandated that by 1998 two percent of the vehicles lighter than 1700 kg sold by each manufacturer in the state be zero-emission vehicles. This percentage must increase to five percent by the year 2001, and ten percent by the year 2003.
A zero-emission vehicle, given the known, viable technologies for vehicle propulsion, effectively means that such vehicles must be all electric, or electric vehicles (EV""s). Hence, if existing (and future) governmental mandates are to be met, there is an urgent need in the art for a viable EV that can operate efficiently and safely.
EV""s are not new. They have existed in one form or another since the discovery of electrical batteries and electric motors. In general, EV""s of the prior art are of one of two types: (1) those thatxe2x80x94through rail or overhead wirexe2x80x94are in constant contact with an external source of electrical power (hereafter xe2x80x9cexternally-poweredxe2x80x9d EV""s); or (2) those that store electrical energy in a battery and then replenish the stored energy when needed (hereafter xe2x80x9crechargeable battery-drivenxe2x80x9d EV""s).
Externally-powered EV""s require their own power delivery system, e.g., electrified rails or electrified overhead wires, that forms an integral part of their own roadway or route network. Examples of externally powered EV""s are subways, overhead trolley systems, and electric rails (trains). Such externally-powered EV systems are in widespread use today as public transportation systems in most large metropolitan areas. However, such systems typically require their own highly specialized roadway, or right-of-way, system, as well as the need for an electrical energy source, such as a continuously electrified rail or overhead wire, with which the EV remains in constant contact. These requirements make such systems extremely expensive to acquire, build and maintain. Moreover, such externally-powered EV systems are not able to provide the convenience and range of the ICE automobile (which effectively allows its operator to drive any where there is a reasonable road on which the ICE vehicle can travel). Hence, while externally-powered EV systems, such as subway, trolley, and electric rail systems, have provided (and will continue to provide) a viable public transportation system, there is still a need in the art for a zero-emission vehicle (ZEV) system that offers the flexibility and convenience of the ICE vehicle, and that is able to take advantage of the vast highway and roadway network already in existence used by ICE vehicles.
Rechargeable battery-driven EV""s are characterized by having an electrical energy storage device onboard, e.g., one or more conventional electrochemical batteries, from which electrical energy is withdrawn to provide the power to drive the vehicle. When the energy stored in the batteries is depleted, then the batteries are recharged with new energy. Electrochemical batteries offer the advantage of being easily charged (using an appropriate electrical charging circuit) and readily discharged when powering the vehicle (also using appropriate electrical circuity) without the need for complex mechanical drive trains and gearing systems. Unfortunately, however, such rechargeable battery-driven EV""s have not yet proven to be economically viable nor practical. For most vehicle applications, such rechargeable battery-driven EV""s have not been able to store sufficient electrical energy to provide the vehicle with adequate range before needing to be recharged, and/or to allow the vehicle to travel at safe highway speeds for a sufficiently long period of time. Disadvantageously, the energy density (i.e., the amount of energy that can be stored per unit volume) of currently-existing electrochemical batteries has been inadequate. That is, when sufficient electrical storage capacity is provided on board the vehicle to provide adequate range, the number of batteries required to provide such storage capacity is prohibitively large, both in volume and weight. Moreover, when such batteries need to be recharged, the time required to fully recharge the batteries is usually a number of hours, not minutes as most vehicle operators are accustomed to when they stop to refill their ICE vehicles with fuel. Further, most currently-existing electrochemical batteries are not suited for numerous, repeated recharges, because such batteries, after a nominal number of recharges, must be replaced with new batteries, thereby significantly adding to the expense of operating the rechargeable battery-driven EV. It is thus evident that what is needed is a rechargeable battery-driven EV that has sufficient energy storage capacity to drive the distances and speeds commonly achieved with ICE vehicles, as well as the ability to be rapidly recharged within a matter of minutes, not hours.
EV systems are known in the art that attempt to combine the best features of the externally-powered EV systems and the rechargeable battery-driven EV systems. For example, rather than use a battery as the energy storage element, it is known in the art to use a mechanically coupled flywheel, i.e., a flywheel that is mechanically coupled to vehicle""s drive train, that is rapidly charged up to a fast speed at select locations along a designated route. See, e.g., U.S. Pat. No. 2,589,453 issued to Storsand, where there is illustrated an EV that includes a mechanical flywheel that is recharged via an electrical connection at a charging station.
Further, in U.S. Pat. No. 4,331,225, issued to Bolger, there is shown an EV that has an electrochemical battery as the preferred storage means, and that receives power from a roadway power supply via inductive coupling. An onboard power control system then provides the power to the storage means, and the storage means then supplies power as needed to an electric motor providing motive power for the vehicle. Bolger also indicates that the storage means could be a mechanical flywheel.
In U.S. Pat. No. 4,388,977, issued to Bader, an electric drive mechanism for vehicles is disclosed that uses a pair of electric motors as motive power for the vehicle. A mechanical flywheel is mechanically connected to the drive shaft of one of the electric motors. The vehicle receives power from an overhead power supply, e.g., trolley lines, and the motor then spools up the mechanical flywheel. The mechanical flywheel is then used to supply power to the motor at locations where there is not an overhead power supply.
In U.S. Pat. No. 5,224,054, issued to Parry, there is shown a bus-type vehicle having a continuously variable gear mechanism that uses a mechanical flywheel as a power source. The mechanical flywheel is periodically charged by an overhead connection to an electrical supply. The flywheel is mechanically linked to the drive shaft of the vehicle.
In the above systems, the mechanical flywheel is used as the energy-storage element because it can be charged, i.e., spooled up, relatively quickly to a sufficiently fast speed. Disadvantageously, however, the use of such mechanical flywheel significantly complicates the drive system of the vehicle, and also significantly adds to the weight of the vehicle, thereby limiting its useful range between charges. Further, the mechanical flywheel operating at fast speeds may present a safety hazard. What is needed, therefore, is an EV that avoids the use of a flywheel mechanically coupled to the vehicle""s drive system. Further, what is needed is an EV that can receive electrical energy from an external source to rapidly recharge, within a matter of minutes, an onboard energy storage element. Moreover, what is needed is such an EV wherein the onboard energy storage element, once charged or recharged, stores sufficient energy to provide the motive force needed to safely drive the vehicle at conventional driving speeds and distances.
The present invention addresses the above and other needs by providing an improved roadway-powered electric vehicle system that includes: (1) an all-electric vehicle; and (2) a roadway network over which the vehicle travels. The all-electric vehicle includes one or more onboard energy storage elements or devices that can be rapidly charged or energized with energy obtained from an electrical current. The vehicle further includes an on-board power controller that extracts energy from the energy storage elements, as needed, and converts such extracted energy to electrical energy used to propel the electric vehicle. Advantageously, the energy storage elements of the vehicle may be charged while the vehicle is in operation. Such charging occurs, e.g., through a network of power coupling elements embedded in the roadway. As the vehicle passes over such power coupling elements, as it traverses the roadway network, electrical current is coupled to the electric vehicle, which electrical current is then used to charge the energy storage devices. Advantageously, such power coupling elements may be coils embedded at strategic locations in existing roadways and highways. Such embedding can be done at a very modest cost.
In a preferred embodiment, the power coupling elements embedded in the roadway comprise a network of coils connected to a conventional primary power source, e.g., single-phase, 2000 to 3500 Hz or 8500 to 9000 Hz electrical power generated by a power conditioner from three-phase 50 or 60 Hz, 480 volt power, as is readily available from public utility power companies or cooperatives. Advantageously, such coils need not be distributed along the entire length of the roadway, but need only be located at selected locations along the length of the roadway, amounting to, e.g., 10% or less of the entire length of the roadway, e.g., 1% of the roadway. A 2000 Hz to 3500 Hz, or 8500 to 9000 Hz alternating electrical current (ac current) is inductively coupled from the power coupling elements embedded in the roadway to a power pickup element carried on the vehicle as the vehicle passes over the power coupling elements. Such ac current, when received in the power pickup element on the vehicle, is then used to charge or energize the storage elements carried by the vehicle.
A power meter, carried onboard the vehicle, monitors how much power is transferred to or used by the vehicle. Hence, the public utility (or other power company) that provides the primary power to the power coupling elements embedded in the roadway (or otherwise located to couple power to the vehicle) is able to account for the electrical power used by the RPEV and to bill the vehicle owner an appropriate amount for such power, thereby recouping the cost of generating and delivering such electrical power.
In some embodiments, the rapid charge energy storage elements or devices carried onboard the electric vehicle comprise an electromechanical battery (EMB), or a group or network of EMB modules. An EMB is a special type of energy-storage device having a rotor, mounted for rapid rotation on magnetic bearings in a vacuum-sealed housing. Because magnetic bearings are used, the shaft of the rotor does not physically contact any other components. Hence, there is no friction loss in the bearings. Because the rotor is housed in a sealed, evacuated, chamber, there are no loses due to windage. As a result, the rotorxe2x80x94made from high-strength graphite-fiber/epoxy compositexe2x80x94is able to rotate at extremely high speeds, e.g., 200,000 rpm. Because the EMB""s rotor is able to rotate at such speeds, high amounts of energy can be stored in a very compact or small volume representing a significant improvement in energy density relative to conventional electrochemical batteries.
In order to store energy in the EMB, and in order to extract energy therefrom, a special dipolar array of high-field permanent magnet material is mounted on the rotor. The resulting magnetic field from such array, extends outside of the sealed housing to cut through stationary, external coils, wound external to the housing. By applying an appropriate ac current to the external coils, the rotor is forced to spin. Because of the compactness and special design of the rotor, it is able to achieve high rotational speeds very rapidly (within minutes). Hence, the EMB may be charged to store a high amount of energy in a very short time, commensurate with the same time it takes to fill the gas tank of existing ICE vehicles.
Advantageously, the rapid charging EMB does not have any direct mechanical linkages with the vehicle""s drive train. Rather, the EMB is charged by simply applying an appropriate ac electrical signal to its terminals. Similarly, the EMB is discharged (energy is withdrawn therefrom) by simply using it as a generator, i.e., connecting its electrical terminals to a suitable load through which an electrical current may flow. Thus, the complexity of the charging components and the discharging components is greatly simplified, and the EMB appears, from an electrical point-of-view, as a xe2x80x9cbatteryxe2x80x9d, having an electrical input and an electrical output.
In operation, the input ac voltage applied to the terminals of the EMB spools up the rotor of the EMB to a rate proportional to the frequency of the applied ac voltage, just as if the EMB were an ac motor. The energy stored in the EMB is in the form of kinetic energy associated with the rapid rotation of the rotor. When extracting energy, the rapid rotating magnetic field, created by the rapid rotation of the magnetic array on the rotor, cuts through the stationary windings, inducing an ac voltage, just as though the EMB were an ac generator. Such induced voltage thus represents the extracted energy. The extracted voltage, in turn, is then used, as needed, to drive the electrical motors that propel the vehicle. Thus, the EMB functions as a motor/generator depending upon whether electrical energy is being applied thereto as an input (motor), or withdrawn therefrom as an output (generator). Unlike a conventional motor/generator, however, the extremely high rotational speeds of the EMB rotor allow great amounts of energy to be stored thereinxe2x80x94sufficient energy to provide the motive force for the EV over substantial distances and at conventional speeds.
Hence, without any direct mechanical linkage to the vehicle""s drive train, the EMB can be electrically charged (i.e., its rotor is spun-up to rapid rotational velocities) using electrical current that is inductively coupled to the vehicle through the roadway over which the vehicle travels. Also without any direct mechanical linkage, the EMB can be electrically discharged (i.e., energy is withdrawn from the rapidly spinning rotor) by having the rotating magnetic field induce a voltage on the stationary windings, which induced voltage powers the electrical drive system of the vehicle.
Advantageously, an EMB may be manufactured as a standardized EMB module, and several EMB modules may then be connected in parallel, as required, in order to customize the available energy that can be stored for use by the EV to the particular application at hand. For example, a relatively small EV, equivalent in size and weight to a xe2x80x9csub-compactxe2x80x9d or xe2x80x9ccompactxe2x80x9d vehicle as is commonly used in the ICE art, may require only two to six EMB modules. A larger or more powerful EV, equivalent in size to a passenger van or high performance vehicle, may utilize 6 to 10 or more EMB modules. A still larger and more powerful EV, equivalent, e.g., to a large bus or truck, may utilize 12-20 or more EMB modules.
Standardizing the EMB module results in significant savings. The cost of manufacturing a standard EMB module, as opposed to many different types of EMB modules, is significantly reduced. Further, maintenance of the EV is greatly simplified, and the cost of replacing an EMB within the EV when such replacement is needed is low.
Additionally, a high operating efficiency is advantageously achieved when an EMB is used as the energy storage element. For example, in an EMB, the entire generator/motor assembly is ironless. Hence, there are low standby losses (no hysteresis effects). In combination with the frictionless magnetic bearings and windless evacuated chamber wherein the rotor spins, this means that the overall efficiency of the EMB should exceed 90%, and may be as high as 95% or 96%. Such high efficiencies result in significantly reduced operating costs of the EV.
When inductive coupling is used to transfer power from the power coupling element (e.g., coils) imbedded in the roadway to the power pickup element (e.g., coils) in the EV, the preferred coupling frequency of the ac current is in the 2000 to 35000 Hz or 8500 to 9000 Hz ranges. The use of such frequency, significantly higher than the conventional 60 Hz or 400 Hz ac signals that are commonly used in the prior art for power coupling purposes, advantageously optimizes the coupling efficiency of the power signal and operation of the EV system. Moreover, by using an ac signal within this frequency range, the magnitude or intensity of any stray magnetic fields that might otherwise penetrate into the vehicle or surrounding areas (as electrical power is inductively coupled into the vehicle) is significantly reduced. Having the magnetic fields that penetrate into the vehicle or surrounding areas be of low magnitude may be an important safety issue, at least from a public perception point-of-view, as there has been much debate in recent years concerning the possible harmful effects of over-exposure to magnetic field radiation. See, e.g., U.S. Pat. No. 5,068,543.
It is thus a feature of the present invention to provide an efficient, viable, safe, roadway-powered all electric vehicle.
It is an additional feature of the invention, in some embodiments, to provide such an EV that uses, with only minor modification, the existing network of highways, roadways, loading/unloading and/or garaging/parking facilitates that are already in place to serve ICE vehicles.
It is yet another feature of the invention, in some embodiments, to provide an EV system wherein the EV""s of the system may be recharged while such EV""s are in operation within the system. Hence, the EV""s need not be taken out of service from the system in order to be recharged, as is common with prior art battery-storage type EV""s.
It is an additional feature of the invention, in some embodiments, to provide an EV, or EV system, wherein the EV uses a high energy density battery or a group of such batteries as an onboard energy storage element. In one embodiment, the battery(s) are electromechanical batteries that due to the use of magnetic bearings and enclosing the rotor in a sealed vacuum chamber, are able to run at extremely high speeds (e.g., exceeding 100K-200K rpm), and thereby provide a large amount of power in a relatively small space.
It is a further feature of the invention, in some embodiments, to provide an EV system that powers a fleet of electrically-powered buses, or other mass transit electric vehicles, using a demand responsive charging system or scheme. In accordance with such scheme, existing highways and roadways over which the EV""s travel are electrified only at select locations, such as: (1) at designated xe2x80x9cstopsxe2x80x9d of the vehicle, e.g., at designated passenger loading/unloading zones, parking garages, or the like; (2) at locations where the vehicle regularly passes, such as roadway intersections; and/or (3) along selected portions of the route, e.g., 50-100 meters of every kilometer over which the vehicle travels.
It is still another feature of the invention, in some embodiments, to provide an EV system that uses inductive coupling to couple electrical power between embedded coils in the roadway and coils carried in a power pickup element carried onboard the EV. Such coupled electrical power is stored onboard the EV and is thereafter used to provide the motive force of the EV. In accordance with related embodiments of the invention, onboard systems and methods are provided that laterally and vertically position the relative spacing and alignment between the onboard coil and the coils embedded in the roadway in order to minimize the air gap between the coils and to maximize the alignment between the coils, thereby making the power transfer from the roadway to the vehicle more efficient. Moreover, using such onboard systems and methods, when the EV is stopped, the air gap may advantageously be minimized to zero.
It is an additional feature of the invention, in various embodiments, to provide an EV that utilizes an on-board control module to perform and coordinate the functions of: (i) receiving the inductive power from the coils embedded in the roadway, (ii) storing the received power as energy in the onboard storage elements, e.g., EMB""s, and (iii) selectively extracting the stored energy to power the vehicle.
It is yet a further feature, in several embodiments, to provide an EV that includes an onboard power meter that monitors the amount of electrical power that has been transferred to the EV as it operates on the electrified network of highways and roadways, thereby providing a convenient mechanism for a utility company, that provides the electrical power to the electrified network of highways and roadways to recoup its energy costs.
In addition to the above-identified features, numerous add-on features may be included as part of the EV system to further enhance its viability. The add-on features may include, for example: (a) establishing a wide bandwidth communications channel with the EV""s that permits numerous communications functions (such as telephone, video, roadway-condition communications, position information communications, and automated, demand-based dispatch) to be carried out via the embedded coils over which the vehicle travels and associated interconnecting power lines, or via a radio frequency communications link or the like; (b) providing fully automated garaging features that permit the onboard EMB""s (and/or other storage elements) to be intelligently charged when the vehicle is parked overnight or at other times in a specially-equipped garage or parking area; (c) platooning of RPEV""s by producing an electronic (cabled and/or radio frequency) or optical coupling between a plurality of roadway-powered vehicles, with one of the vehicles being a xe2x80x9cmasterxe2x80x9d or leader, and the others being xe2x80x9cslavesxe2x80x9d or followers that follow the master, to provide, in effect a roadway-powered xe2x80x9ctrainxe2x80x9d; (d) using inductive or ohmic heating coils, powered by the same power source that couples power into the vehicle from the roadway, to melt snow or ice in the vicinity of a passenger loading/unloading zone and/or from the surface of the power coupling element; (e) ergonomically designing a passenger compartment of the EV to facilitate passenger loading, unloading, seating, and safety; (f) using an onboard lateral guidance system to not only position the EV for optimal power transfer between the power coupling element and the power pickup element, but to position the EV for elevator-like platform loading (which can require controlling the position of the EV to within a few centimeters); (g) providing electronic actuators for steering and braking so that, when the EV is operating as a xe2x80x9cslavexe2x80x9d or follower, reaction time to command signals from the xe2x80x9cmasterxe2x80x9d or leader is minimized; (h) utilizing the wide-band communications system or the like, in combination with a scheduling and dispatch computer, for performing dispatch functions and the coordination of scheduling in a public transportation system based on demand; (i) precisely determining the position of the EV in response to a location signal from a global positioning system (GPS) or Differential GPS (dGPS) receiver, preferably in combination with a dead-reckoning (i.e., inertial) locating system, in order to (1) provide a backup position indication for electrically or optically coupled EV""s, (2) provide either primary or backup position information for lateral alignment of the power pickup element over the power coupling element and/or for xe2x80x9celevator-likexe2x80x9d platform loading; and (j) wayside control of the EV""s through an xe2x80x9cATM-likexe2x80x9d control station for (1) dynamically displaying scheduling information, (2) summoning free-roaming point-to-point EV""s (i.e., taxis or limousines), and (3) providing demand-based scheduling including monitoring the number of passengers on an EV and adjusting dispatch/scheduling in response thereto; (k) maintaining communications with the EV during electronic garaging in order to communicate, e.g., to the vehicle""s owner whether the vehicle has been tampered with; (1) providing a kneeling feature for public transportation EV""s that lowers (or xe2x80x9ckneelsxe2x80x9d) the entire vehicle for loading/unloading, and simultaneously reduces the air gap between the power pickup element and the power coupling element to zero or near zero; and (m) providing for route memorization by recording a dGPS location signal as the vehicle manually driven over a route so that the vehicle can subsequently automatically navigate the route.